First record of Faxonius propinquus (Girard, 1852) in the Delaware River watershed and new records of another non-native crayfish species, Procambarus acutus (Girard, 1852)

Abstract

Faxonious propinquus is considered native to the Susquehanna River watershed but is not native to the nearby Delaware River watershed in North America. Here we show that Faxonious propinquus is now established in the Delaware River watershed, which is reason for concern. We also provide published records to describe more fully the distribution of Procambarus acutus, a species considered non-native in the Delaware River when found upstream of the Atlantic Coastal Plain. We provide evidence that indicates that F. propinquus has become established in the Lehigh River, a subwatershed in the Upper Delaware River, and that P. acutus has expanded into this portion as well. In addition, we provide evidence of hybridization occurring between the native Faxonius limosus and a non-native congener.